Stain resistance, water repellency and resistance to microbial growth are important in many uses of textile materials. In restaurants, for example, table cloths and seating upholstery often lack stain resistance and are subject to rapid water penetration. These properties necessitate frequent cleaning and/or replacement of such items. Although one generally views microbial growth as associated with fibers of biologic origin such as cotton, wool, linen, and silk, in the field of marine use, the high relative humidity renders even synthetic polymer textiles such as polyesters and polyamides subject to microbial growth, which is also true of many other outdoor uses.
Water repellant textile fabrics may be made by various processes. The term "water repellant" as used herein means essentially impermeable to water, i.e. treated textile can support a considerable column of water without water penetration through the fabric. Such behavior is sometimes termed "water resistant." However, the last term generally implies a lesser degree of water repellency and further can be confused with the chemical use of "water resistant" to refer to coatings which are chemically stable to water or which will not be washed off by water. Hydrophobicizing topical treatments are incapable of providing the necessary degree of water repellency as that term is used herein.
Waxes and wax-like organic compounds have often been used to provide limited degrees of water repellency. For example, textile fabrics may first be scoured with a soap solution and then treated with a composition which may include zinc and calcium stearates as well as sodium soaps. The long chain carboxylic acid hydrophobic compounds provide a limited amount of water repellency. It is also possible to render fabrics liquid resistant by treating the fabric with commercially available silicones, for example poly(dimethylsiloxane). In tenting fabrics, use is commonly made of paraffin waxes, chlorinated paraffin waxes, and ethylene/vinyl acetate copolymer waxes. Typical of such formulations are those disclosed in U.S. Pat. No. 4,027,062, a wax-based organic solvent-borne system; and U.S. Pat. No. 4,833,006, which employs a wax-based, organic solvent-borne system further containing an unblocked polyisocyanate as an adhesion promoter. The use of the unblocked isocyanate is said to decrease the peeling or flaking off of the coating as compared to wax-based systems employing blocked isocyanate-terminated prepolymers as disclosed in U.S. Pat. No. 4,594,286. Such treated fabrics have a coarse, waxy hand and feel, exhibit little water vapor permeability, are not resistant to organic solvents, and are limited in the manner in which they can be printed.
To overcome problems associated with water absorption and stain resistance, particularly in upholstery materials, resort has been made to synthetic leathers and polyvinylchloride (vinyl) coated fabrics. However, these fabrics do not have the hand or feel of cloth, and in general, are difficult and in many cases impossible to print economically. Moreover, although attempts have been made to render such materials water vapor permeable, these attempts have met with only very limited success, as evidenced by the failure of synthetic leather to displace real leather in high quality seating and footwear. For example, U.S. Pat. No. 4,507,413 discloses leather-like coatings prepared from an aqueous dispersion of a blocked, isocyanate-terminated polyurethane containing a water soluble thickener. The top coating is coated onto a release paper, cured with diamine, and then bonded with the aid of a bonding coat to a fabric support. Following removal of the release paper, a grained, leather-like coating is obtained. In U.S. Pat. No. 5,177,141, similar coatings are disclosed which, in addition, require a water immiscible solvent to be dispersed with the polyurethane, and further requires the presence of a hydrophilic polyisocyanate to promote adhesion to the textile substrate. The presence of the water-immiscible solvent produces a pore-containing material by evaporative coagulation, leading to high water vapor permeability.
Although the treating and coating methods discussed previously may assist in rendering the fabric partially liquid and/or stain resistant, the leather-like appearance of fabrics coated as disclosed by U.S. Pat. Nos. 4,507,413 and 5,177,141 is not desired in many fabric applications. Despite their higher water vapor permeability as compared to earlier generation synthetic leathers, such products are still uncomfortable in many seating upholstery applications. Furthermore, fabrics treated or coated with wax-like polymer or wax emulsions cannot be satisfactorily printed. The treated liquid resistant fabrics may refuse to accept or become incompatible with the application of color dyes. The polymeric coated liquid resistant fabrics cannot be transfer printed because the heat required in the printing process generally causes the polymeric coating to melt or deform. Thus, if a fabric with a particular design or logo is required, the textile fabric must be printed first by traditional methods, following which it may be treated or polymer coated. However, the polymer coating generally obscures the design due to its thickness and opacity, even when non-pigmented vinyl, for example, is used.
Applications of relatively small amounts of fluorochemicals such as the well known SCOTCHGUARD.TM. and similar compounds also may confer a limited degree of both water resistance and stain resistance, as discussed previously. However, for optimal water repellency, it has proven necessary to coat fabrics with thick polymeric coatings which completely destroy the hand and feel of the fabric. Examples include vinyl boat covers, where the fabric backing is rendered water resistant by application of considerable quantities of polyvinylchloride latex or the thermoforming of a polyvinyl film onto the fabric. The fabric no longer has the hand and feel of fabric, but is plastic-like. Application of polyurethane films in the melt has also been practiced, with similar results. However, unless aliphatic isocyanate-based polyurethanes are utilized, the coated fabric will rapidly weather.
Coatings of polyurethanes or polyurethane ureas have been disclosed in numerous patents and publications. However, the majority of these coatings, such as those previously described, produce fabrics whose hand and feel is not acceptable, i.e. are synthetic leather-like in appearance. Moreover, in producing non-leather-like fabrics coated with polyurethane, it is generally necessary to dissolve the polyurethane into a solvent, and apply this solution to the fabric. Polyurethane lattices, in general, have not been used to provide a fabric with a soft feel, because the prepolymer viscosity of polyurethanes necessary to provide soft coatings is so high that dispersions cannot be prepared. Thus, solvent-borne polyurethanes have been used. Unfortunately, it is increasingly difficult to utilize solvent-borne coatings of any kind in both industrial and domestic applications due to pollution laws. Examples of the foregoing coatings are disclosed in Japanese patent JP 06108365 A2, "Moisture Permeable Water-Resistant Polyurethane-Coated Fabrics And Their Manufacture"; U.S. Pat. No. 5,306,764, "Water Dispersable Polyurethane-Urea Coatings And Their Preparation"; Japanese patent JP 06031845, "Manufacture of Water-Resistant Moisture-Permeable Laminated Fabrics"; European published application EP 525671 A1, "Water-Borne Resin Compositions and Automobile Interior Fabrics Coated With Same"; Japanese patent 03-195737 A2, "Aqueous Polyurethane Acrylate Dispersions"; German patent DE 3 836 030 A1, "Aqueous Polyurethane Dispersions For Moisture-Permeable Coatings"; U.S. Pat. No. 4,889,765, "Ink-Receptive, Water-Based Coatings"; Japanese patent JP 01097274 A2, "Moisture-Permeable Waterproof Sheets"; John C. Tsirovasiles et al., "The Use of Water-Borne Urethane Polymers in Fabric Coatings", J. Coated Fabrics Oct. 16, 1985, pp. 114-22; Weinberg, Joseph W., "Performance and Application Advantages of Water-Borne Systems In Automotive And Textile Industries", J. Industrial Fabrics (1986) 4(4), pp. 29-38; German patent DE 34 15 920 A1, "Aqueous Dispersions For Coating of Textiles"; and German patent DE 323 10 62 A1, "Aqueous Dispersions of Reactive Polyurethanes for Coatings".
The foregoing references all produce fabrics with severe deficiencies in numerous areas. The most severe deficiency in many of these fabrics is the inability to be transfer-printed. Transfer printing requires elevated temperatures at which the bulk of these coatings melt and adhere to the transfer printing drum. The inability to be transfer-printed requires that the fabrics be printed by conventional textile printing methods. However, the use of such methods is impractical in short runs of less than, for example, 10,000 meters of material. Thus, it is impossible to economically produce unique designs in short runs of fabric.
It would be desirable to provide a fabric that allows water vapor to pass through the fabric while prohibiting the passage of liquid. It would also be desirable to provide a method of producing a liquid repellant, strain resistant, antimicrobial fabric. It would further be desirable to provide a liquid repellant, stain resistant, antimicrobial fabric that retains its natural hand and texture, is easy to handle, and economical to produce. It would be yet further desirable to provide a method of producing a liquid repellant, stain resistant, antimicrobial fabric that may be transfer printed.